package flyingpig.hibernate;

import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

/**
 * Configures and provides access to Hibernate sessions, tied to the current
 * thread of execution. Follows the Thread Local Session pattern, see
 * {@link http://hibernate.org/42.html}.
 */
public class HibernateUtil
{

    /**
     * Location of hibernate.cfg.xml file. NOTICE: Location should be on the
     * classpath as Hibernate uses #resourceAsStream style lookup for its
     * configuration file. That is place the config file in a Java package - the
     * default location is the default Java package.<br>
     * <br>
     * Defaults: <br>
     * <code>CONFIG_FILE_LOCATION = "/hibernate.conf.xml"</code> You can
     * change location with setConfigFile method session will be rebuilded after
     * change of config file
     */
    private static String CONFIG_FILE_LOCATION = "/hibernate.cfg.xml";

    private static final ThreadLocal threadLocal = new ThreadLocal();

    private static Configuration configuration = new Configuration();

    private static SessionFactory sessionFactory;

    private static String configFile = CONFIG_FILE_LOCATION;

    private HibernateUtil()
    {
    }

    /**
     * Returns the ThreadLocal Session instance. Lazy initialize the
     * <code>SessionFactory</code> if needed.
     * 
     * @return Session
     * @throws HibernateException
     */
    public static Session getCurrentSession() throws HibernateException
    {
        Session session = (Session) threadLocal.get();

        if (session == null || !session.isOpen())
        {
            if (sessionFactory == null)
            {
                rebuildSessionFactory();
            }
            session = (sessionFactory != null) ? sessionFactory.openSession()
                    : null;
            threadLocal.set(session);
        }

        return session;
    }

    /**
     * Rebuild hibernate session factory
     * 
     */
    public static void rebuildSessionFactory()
    {
        try
        {
            configuration.configure(configFile);
            sessionFactory = configuration.buildSessionFactory();
        } catch (Exception e)
        {
            System.err.println("%%%% Error Creating SessionFactory %%%%");
            e.printStackTrace();
        }
    }

    /**
     * Close the single hibernate session instance.
     * 
     * @throws HibernateException
     */
    public static void closeCurrentSession() throws HibernateException
    {
        Session session = (Session) threadLocal.get();
        threadLocal.set(null);

        if (session != null)
        {
            session.close();
        }
    }

    /**
     * return session factory
     * 
     */
    public static SessionFactory getSessionFactory()
    {
        return sessionFactory;
    }

    /**
     * return session factory
     * 
     * session factory will be rebuilded in the next call
     */
    public static void setConfigFile(String configFile)
    {
        HibernateUtil.configFile = configFile;
        sessionFactory = null;
    }

    /**
     * return hibernate configuration
     * 
     */
    public static Configuration getConfiguration()
    {
        return configuration;
    }

}